This invention relates generally to lint removal systems for clothes dryers. In a conventional dryer, heated air is forced through a rotating drum for evaporating moisture from damp clothes tumbling therein. Air expelled from the drum carries away moisture in addition to lint particles imparted from the clothes. The expelled air is channeled through a duct which is adapted to provide an operator accessible location for a lint filter or screen disposed within the expelled air stream. Airborne lint is accumulated upon the screen during the drying cycle which requires periodic removal.
The manual lint removal required by the above approach may be burdensome, particularly in a commercial setting such as a self-service laundry. Further, degradation of dryer performance occurs during the drying cycle as lint accumulation progressively impedes expelled air flow.
A number of approaches have been attempted to remove lint automatically thereby eliminating the need for manual removal. Various systems have been proposed wherein lint is accumulated in the discharge duct by screen filters, or centrifugal separators, and then incinerated by a separate heat source. By requiring a separate heat source, in addition to the heat source for heating drying air, the overall efficiency of these systems is impaired.
In another approach, U.S. Pat. No. 2,809,025 discloses the incineration of lint by diverting hot gases from the dryer burner through a bypass tube into the discharge duct. A rotating screen collects lint within the duct, the lint being combusted as the screen rotates past the bypass tube. This approach has several disadvantages. First, hot gases, which otherwise would be utilized for drying clothes, are diverted directly into the exhaust duct. Second, the combustion gases are cooled as they travel throuch the bypass tube. Hence, lint combustion may produce unacceptable levels of ash and carbon residues.
An approach wherein lint is incinerated directly by the dryer burner is shown in U.S. Pat. No. 3,306,596. Air expelled from the drum is channeled through an outlet duct to an outside flue. A portion of the outlet duct is positioned adjacent to the burner area thereby enabling a rotating disc or lint filter to communicate between the duct and burner area. Expelled air passes axially through the disc depositing lint thereon which is combusted as the disc rotates through the burner area. This approach has significant disadvantages. First, the rotating disc assembly requires additional drive components. Second, if the disc fails to properly rotate the expelled air flow will be impeded resulting in degradation of performance and a possible fire hazard.
An additional problem with all of the prior approaches to lint removal is that the ducting required for placement of lint filters, or the placement of lint incineration devices, has added to the size, complexity and thermal mass of the dryer.